All life on Earth shares a number of common features. For example, all life on Earth contains DNA that uses the same set of amino acids.
People who support evolution say that this is evidence of common ancestry.
Creationists claim that this is evidence of a common designer.
Creationists support their claim by pointing out that human intelligent designers often use the same components in different designs.
What are the reasons that humans use the same components?
I believe that my own engineering experience – more than 40 years worth – can help answer this question.
Human engineers use common components in different designs for two reasons.
First, it saves money. If General Motors can use the same bolt in both a Chevrolet and a Cadillac, then that bolt can be purchased in larger quantities from the manufacturer and the cost of each bolt will go down. Therefore the cost to build both the Chevrolet and the Cadillac will go down as well. The cost of a single bolt won’t make much difference, but as you make common use of more and more components the total cost savings can become appreciable.
Second, once a component has been used (and reused) the “bugs have been worked out” (as engineers are fond of saying). Humans are imperfect designers and their initial designs often contain flaws. Some of those flaws only become apparent when the component has been put into production. Automobiles, for example, sometimes must be recalled and components replaced because of such design flaws.
However, the more often a component is used, the more it is tested in production environments. Eventually the design flaws are eliminated. Implementing an entirely new component that had never been used before would introduce an element of risk that wouldn’t be present with a component that had been used over and over again.
The expression used by engineers is: "Don't redesign the wheel".
Because of the cost savings and improved component reliability, engineers are often asked during design reviews to reuse existing components. A common statement that you will hear from an engineer is something like, “Yeah. I think that I can make that work.” In other words, the engineer often reuses another component but does so as a compromise.
Of course, an omnipotent, omniscient designer would not be influenced by either of these factors.
Consider DNA. It is comprised of four different bases: adenine (abbreviated A), cytosine (C), guanine (G) and thymine (T). It is comprised of those same four bases in all life on Earth.
What if it consisted of a different four bases in different organisms? What if it consisted of six different bases? Or eight or more different bases?
A human engineer would be told that using a different set of bases in different organisms or using more than this four in any particular organism would cost money and would be discouraged. But such a cost would not be apparent in biology. So this factor would not influence an omnipotent, omniscient designer.
A human engineer would also be told that these four bases have been proven to work over billions of years so they have been proven reliable. That would also not be a consideration for an omnipotent, omniscient designer – especially if that designer was able to modify the physical laws of the universe.
Of course, using more bases would seem to be a more efficient design. It would allow genes to be developed using fewer base-pairs than there are now.
One way to look at this is to compare it to language with the four bases comprising the letters of that language in DNA. The English language has 26 letters. Other languages have more (or fewer) letters. The more letters that are available in a language, the larger the number of combinations (i.e. words) that are available in that language.
If the language consists of only four letters, then there are only four times four or 16 different possible two-letter words. If, like English, there are 26 letters available, then it possible to construct 26 times 26 or 676 different two-letter words. As the number of letters allowed per word increases, so does the number of available combinations.
Similarly, having more than four bases to “spell out” the various genes would be much more efficient.
More interestingly, while I’m not multilingual myself, I have been told that some languages allow you to express thoughts that can’t be expressed as easily in other languages. I tend to believe this claim because languages adopt words or phrases from other languages because the adopting language doesn’t have a way of expressing that same message.
The French phrase “déjà vu” which means, of course, the feeling that we’re experiencing something that we had experienced previously, is an example of this. There are, of course, many others.
All of this leads me, as a professional engineer, to believe that an omnipotent, omniscient designer would use different components in designs that were very much unlike each other.
Plants and animals are very different from each other. I seriously doubt that even a human designer would use the same components in both types of living organisms. An omnipotent, omniscient designer not laboring under the constraints of humans is even less likely to do so.
Furthermore, let’s turn the argument around. Let’s say that plants and animals did have completely different “components”. That would be hugely significant. There would be effectively no way for evolution to claim common ancestry if that were the case.
So, at the very least, this omnipotent, omniscient designer is certainly making it look like all life on Earth evolved from a common ancestor. At a minimum, therefore, the contention of creationists that this is the result of the work of a common designer implies that the designer is a bit deceptive. The use of different “components” in living things would make it obvious that they had not evolved from a common ancestor.